The development of an effective lubrication procedure is the backbone of a successful, World-Class maintenance program. Once developed, this procedure can be expanded into the method by which all of the bearings in your unique process receive the proper lubrication.
A well-designed lubrication procedure must address three separate and distinct issues. Specifi cally, each bearing must receive the correct type of lubrication in the proper amount at the right time. If any one of these three factors is overlooked or approached incorrectly, the lubrication procedure has failed, and, as a result, the bearing will fail prematurely.
Type of lubrication…
Any Maintenance Manager worth his or her salt will be able to identify most or all of the offi cial lubricants on the plant site. Still, the authorized list of lubricants is only part of your maintenance reality. Most management-sanctioned lubricant lists contain redundant and unnecessary choices due to years of supplier and vendor recommendations combined with the preferences of your maintenance personnel. Additionally, a quick walk through the shop or lube room will, in all likelihood, lead you to discover a great deal more variety in lubricants than you thought you were using. And, if you check a few lockers and tool boxes, you will fi nd even more. Obsolete or out-of-date lubricants, unmarked oils, and unfamiliar and unapproved brands and types—if you fi nd any of these (and you will) your lubrication program is out of control.
As a general rule, the fewer lubricants it takes to sustain a manufacturing process, the better that process is. In other words, the fewer choices your millwrights and lube techs have, the fewer incorrect choices they can make.
It is important to reduce the number of lubricants to the lowest common denominator. Brand names and personal preferences do not matter. The only factors to consider in this selection are the properties of the lubricants and the specifi cations of the bearings that they are to lubricate. Ideally, you should strive to get down to two or three types of grease, one or two types of hydraulic oil, and no more than three types of other oils for your entire process. As a suggestion, have your Maintenance Planner or Reliability Engineer discuss this goal of lubricant consolidation with your lubrication vendor’s factory representatives, as well as with your bearing supplier’s fi eld engineers. Let these professionals be your experts.
Amount of lubrication…
At this moment somewhere in your mill or factory, there is a bearing running hot due to over-lubrication. Also at this moment, there is another bearing in your process running hot due to under-lubrication. Which of these conditions is worse—and which bearing will fail fi rst? The fact is that both conditions are equally as bad, since both are indications of a failed maintenance effort. Moreover, one is just as likely to occur as the other. That said, either condition will cause your process(s) to literally grind to a halt. The key to your maintenance success is to determine the maximum and minimum amounts of lubricant that you must maintain at each application, and then to design your lubrication procedures around those two fi xed points. As a fi rst step to controlling the amounts of lubrication applied to bearings, you will need to calibrate all of the grease guns in your plant. Since the lubrication procedures for bearings should be written in terms of how many shots of grease to apply, it is important to both defi ne and control how much grease is contained in a “shot.” Consistency between grease guns is the goal of calibration. It is important that all of your dispensing devices are applying the same amount of grease when your technician pulls the handle.
It also is important to thoroughly clean the guns inside and out to control contamination—and to discard any that are in poor condition. Each reconditioned and calibrated grease gun should be marked with the date before being placed back in service. You should set up a general PM in your CMMS to perform this function at least twice per year. (The calibration procedure is straightforward. For details, refer to the accompanying sidebar.)
It is the nature of lubricants that they use themselves up as they do their job. Thus, they must be replenished. If this replenishment occurs at the proper intervals, then the moving parts continue to move within specifi cations. But if the interval is not correct, if it is too long or not long enough, then over-lubrication or under-lubrication will be the result. Both conditions are the fi rst phases in the sequence of events that lead to machine failure.
The most accurate method available for determining lube interval is the predictive technology known as vibration analysis. If this methodology is not available or practical at your site, the OEM recommendations supplied with each bearing will be suffi cient to use as your beginning lubrication interval, provided you are not exceeding the bearing manufacturer’s specifi cations and ratings in your application.
Please note that if you are running your process in excess of its rated capacity, you will need to monitor your components with vibration analysis or thermal technology so that you can determine the point at which the component needs re-lubrication, even if you must hire an outside contractor to perform these analyses.
Developing your lube procedure
As with any PM procedure, the lubrication procedure should be developed and written up with a specifi c machine in mind. Once you have developed the procedure for one machine, extrapolate the steps to include other machines in your process.
|Identify all of the lube points at the machine center. This step should be done in the fi eld by the individual who ultimately will be responsible for lubricating the machine. This individual will locate the zerks and lube points on the machineand will call them out to the Maintenance Planner, who will document the locations. Each lube point should be wiped, inspected and marked with a black or yellow paint pen so that they will be easy to locate.|
|As the bearings are inspected, the Planner should make notations of any that have blown seals or that show other evidence of damage or failure. The bearings in question should be scheduled for replacement as soon as it is practical to do so. Any broken or defective grease zerks should be replaced at this time. Once the zerks have been located and cleaned, they should be covered to prevent contamination from entering the bearing or component. Push-on covers can be purchased for this purpose, or the tried-and-true method of putting a fresh daub of clean grease on the zerk can be used.|
|Once the lube point identifi cation has been completed, compare the Planner’s notes to the machine’s drawings and manuals. The last thing that seems to be on engineers’ minds when they are designing machinery is the accessibility of lube points. Thus, it is entirely possible that there are lube points on your machine that have never received any grease at all. If this is the case, now is the time to rectify the problem. Identify any bearings that have been overlooked at this step.|
|Bearing by bearing, calculate the manufacturer’s recommended lubrication intervals and amounts. A good tool to use when performing these computations can be found at the following web address: www.skf.com/skf/productcatalogue/jsp/calculation/ calculationIndex.jsp?&maincatalogue=1&lang=en. Be sure to convert your answer to “shots.”|
|Bearing by bearing, write the procedure. Start at one end of the machine and take the bearings in order. Beside each bearing that you list on the lube document, leave a space for the technician’s initial, the number of shots applied and the date.|
|Lubrication technicians must be trained in the proper methodology before being allowed to perform their work. As an introduction to their training, make them aware that the vast majority of bearing failures are the result of over-lubrication. Be certain that they are equipped with fresh grease, clean rags and a pocketful of replacement zerks when they go out into the fi eld. It is extremely important to build accountability into this training. Lubrication techs are not just grease monkeys. Their work may, in fact, be the most important maintenance function in the plant.|
|Once you have performed your lubrication procedure, you must monitor the results. The most effi cient way to do this is with thermal technology. After the freshly-lubricated bearings have run for an hour or two, check them with a thermal camera. Any that are running hot have been over-lubed. If you determine that this condition is due to a lubrication error by your technician, retrain the individual and document the training. If you feel that the work was done as requested, then you will need to adjust the text of your lube PM accordingly.|
As with most other maintenance functions, a lubrication PM is a living document. Each time your technicians perform such a procedure, follow up their work by checking the results. This fi nal important “step” is vital in the enhancement of your entire maintenance effort.